The Circadian Rhythm of Renin

Abstract

The circadian rhythm of plasma renin activity during continuous recumbency was determined fifty-one times in thirty subjects who either slept at night or remained awake for 24 h. Both groups had maximum values between 2400 and 0800 h, despite absence of the expected early morning fall in blood pressure, pulse, and glomerular filtration rate in the awake subjects. Infusion of normal saline between 2300 and 0300 h initially suppressed renin, but did not prevent its subsequent rise regardless of the amount of sodium appearing in the urine. Of thirteen patients tested two to five times, twelve had recurrence of the zenith within a single 4 h period on retesting, despite differences in sodium intake, basal blood pressure, and mean plasma renin activity. Peaks of lesser magnitude were also frequently noted, most commonly at 1000 h and 1800-2000 h. Minimum PRA values were not restricted to a particular time of day and did not generally recur at the same time upon retesting. The mean ratio of maximum to minimum PRA in each study was 246% +/- 18.3% (+/- 1 SEM). The circadian rhythm of renin appears to be independent of known renal mechanisms responsible for regulating renin release. It is possible that this rhythm is controlled by the central nervous system.

Nyctohemeral Rhythm of Plasma Renin Activity and Plasma Aldosterone in Children

“…The fundamental work of Modlinger er al. (17), showing the persistence of a nocturnal PRA peak in subjects kept awake overnight, clouds previous works and in general the discussions on the role of different time periods of sleep (1 1, 12,22) being at the origin of nocturnal PRA peak. Inasmuch as none of our subjects was kept awake, we can only report that the nocturnal peak occurs almost as frequently at midnight as at 4:00 PM.…”

“…The alternance of a zenith before noon and a nadir in the midafternoon has been reported in daytime studies when plasma samples were obtained only every 3 or 4 hours (2,7,17,24). In contrast, data obtained from studies with more frequent samples showed peaks scattered all over the day without any defmite pattern (1,11,12,15,22).…”

“…More precisely, they inhibited the nocturnal peak by feeding subjects overnight with meals containing sodium. On the other hand, when Modlinger et al (17) infused saline serum to subjects between 11:00 PM and 3:00 AM, the peak appeared at the end of the infusion. Our protocol does not bring any direct evidence to establish definite conclusions on this subject.…”

Lack of inhibition of ACTH-induced aldosterone stimulation by Desasp-, ileu-angiotensin II in man.

“…There is a diurnal variation in PRA during the constant recumbency (Katz et al, 1972;Modlinger et al, 1976). However, it is unlikely that a significant PRA difference exists between0900hr and 1000hr.…”

Exogenous insulin augments in healthy volunteers the cardiovascular reactivity to noradrenaline but not to angiotensin II.

“…After basal blood pressure (the mean of five measurements) was measured and baseline blood samples were drawn, an infusion with either NA (noradrenaline tartrate, Centrafarm, dissolved in 5% dextrose) or All (Hypertensin, Ciba Geigy, dissolved in 5% dextrose) was begun. Each pressor infusion was started at the lowest infusion rate and progressively increased with predetermined steps (NA: 10, 20, 40, 60, 80, 100, 150, 200, 250, 300, 350, 400, 450, and 500 ng/kgpermin;AII: 1,2, 4,6,8,10,12,14,16,18,20,25,30,35,40,45, and 50 ng/kg per min). Blood pressure was measured during each infusion rate every minute and the infusion rate was increased to the next one, without a washout period, only after blood pressure had stabilized for at least 5 min.…”